Page 70 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 4
The surface morphology of the HMT-based coating consisted of well-defined pores with a diameter of 1.3±0.4μm. The total thickness of the coating was of 2.9±0.5μm with a compact barrier layer of 0.7 ±0.1μm. Similarly, MAN- based coatings also showed a uniform distribution of pores, with a diameter of 1.3±0.7μm. The density of the pores by area on the MAN sample looks higher than HMT. The cross-section of the MAN showed a thin compact inner layer of 0.7 ±0.1μm superimposed by the porous layer reaching a total of 4.0 ±0.5μm. It is observed how the morphol- ogy and microstructure of the coatings are highly influenced by the additives in the electrolytes which modifies the conductivity of the solution. Here, variations are mainly observed on the surface and internal porosity, with HMT and MAN increasing both. Also thickness is affected with MAN leading to formation of thicker coatings.
Fig. 3. Surfaces and cross-section views of c.p Mg modified to study morphology and thickness of pro- duced coatings NAF(A, B) coating presented a compact appearance, oppositely porous films were ob- tained by HMT(C, D) and MAN(E, F)
Two-step anodizing surfaces presented higher porosity in comparison with single anodizing (Fig.4). In the case of NAF HMT the surface presents more discontinuities, apparently due to pore coalescence, the average size of the remaining pores was about 1.4±0.9μm. The total thickness for this sample was of 3.2±0.4μm. For NAF MAN the structure was more uniform and similar to the morphology obtained with single MAN, it is possible to observe some larger pores, however the average porous size was of 1.3μm ±0.6; the thickness of this coating was of 4.0±0.4μm. The barrier layer of the NAF HMT sample is thicker than NAF MAN. Internal porosity for these two samples is similar, showing some passing through pores and interconnected porosity located mostly right above the barrier layer.
Fig.4. Morphology and cross-section of two-steps coatings. Interconnected pores on the surfaces of NAF¬HMT (A-B) and NAF¬MAN (C-D) samples.
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